Three hypotheses may explain why species at risk of extinction in the near future are often nonrandomly distributed across clades. First, differences in extinction risk among clades may be positively or negatively related to clade age if extinction probability increases or decreases over time, respectively. Second, clade extinction risk may be negatively related to clade size if larger clades are more likely to contain species that have specific traits required to endure environmental change. Third, if the current extinction patterns resemble those of past mass extinctions during which widespread clades had higher survival probability, then clade extinction risk may be negatively related to the geographic range size of the entire clade. Here, we used Bignonieae as a model group to examine the distribution of extinction risk across clades and test the three hypotheses above. Using herbarium data and IUCN criteria associated with range size to estimate extinction risk, we found that extinction risk was not randomly distributed across Bignonieae clades. Thus, through future extinctions we may lose more Bignonieae evolutionary history than would be expected by the number of species disappearing. Clade extinction risk was not related to clade age nor to clade geographic range, thus offering no support for the first and third hypotheses. On the other hand, clade extinction risk was strongly and negatively related to clade size, but this effect became weaker with increasing clade age. Thus, our results support the hypothesis that clade size reduces extinction risk as it applies to relatively young clades, but also indicate that species richness is not a buffer against extinction for older clades.